A gas analysis system with a radiation source and a Fabry-Perot interferometer is known from DE 10 2006 045 253 B3, wherein the radiation from the radiation source passes through a gas measuring section in the form of a cuvette and then falls through the Fabry-Perot interferometer. The Fabry-Perot interferometer is continuously detuned with a predefined voltage, i.e., the distance of the mirrors oscillates with this voltage, and the radiation being released therefrom is detected and analyzed by a dual-band detector. In this connection, an absorption spectrum is determined by the intensity of the radiation being released from the Fabry-Perot interferometer and falling on the sensor being determined as a function of the wavelength, on which the interferometer is especially sensitive because of the distance of the mirrors.
In gas analysis systems of this type, however, the technical problem arises of achieving a reliable calibration of the sensor and of the measured values resulting from the sensor signal in relation to the wavelength and especially if thermal sensors are used which have long time constants. Such thermal sensors, such as pyroelectric detectors, must, however, frequently be used when radiation that is in the long-wave infrared range, i.e., especially in the range between 5 μm and 12 μm shall be detected. This is especially necessary if the gas analysis system shall be used for the analysis of anesthesia gas, in which the nitrous oxide and carbon dioxide contents in the breathing gas shall be determined.
Thermal sensors have, as already mentioned, a long time constant, so that they react only slowly to a change in the intensity that impinges on them. Hence, an absorption spectrum for a wavelength range with such a sensor in case of changing detuning of the Fabry-Perot interferometers and thus in case of a change in the wavelength, for which the interferometer is sensitive or which is allowed to pass through the interferometer, can only be recorded with a great expenditure of time, which would subsequently have to be analyzed in order to carry out a gas concentration determination. However, this in turn would lead to brief changes in the concentration of the gas to be analyzed being able to be detected with difficulty only.